Missing Apps

I have a problem with my RT. A few days ago when I turned on my RT on I realized that some of the apps were literally missing (including Xbox Music and Skype) And not just from the start screen. I searched for them but it seems like they are not there anymore. I also tried to install them new from the Store, but I still couldn't find them afterwards. Does anyone has experienced something like this before or know how this can happen and how I can fix this?